<!DOCTYPE html>
<html lang="en">
<head>
  <meta charset="UTF-8">
  <title>Title</title>
</head>
<body>
<script>
  new Promise((resolve, reject)=>{
    setTimeout(()=>{
      resolve('Hello World');
      // reject('error message');
    },3000);
  }).then(data=>{
    console.log(data);
  },err=>{
    console.log(err);
  });
</script>
</body>
</html>